1 /* SPDX-License-Identifier: GPL-2.0-only */
2 /*
3  * Copyright 2008-2010 Cisco Systems, Inc.  All rights reserved.
4  * Copyright 2007 Nuova Systems, Inc.  All rights reserved.
5  */
6 
7 #ifndef _CQ_DESC_H_
8 #define _CQ_DESC_H_
9 
10 /*
11  * Completion queue descriptor types
12  */
13 enum cq_desc_types {
14 	CQ_DESC_TYPE_WQ_ENET = 0,
15 	CQ_DESC_TYPE_DESC_COPY = 1,
16 	CQ_DESC_TYPE_WQ_EXCH = 2,
17 	CQ_DESC_TYPE_RQ_ENET = 3,
18 	CQ_DESC_TYPE_RQ_FCP = 4,
19 };
20 
21 /* Completion queue descriptor: 16B
22  *
23  * All completion queues have this basic layout.  The
24  * type_specfic area is unique for each completion
25  * queue type.
26  */
27 struct cq_desc {
28 	__le16 completed_index;
29 	__le16 q_number;
30 	u8 type_specfic[11];
31 	u8 type_color;
32 };
33 
34 #define CQ_DESC_TYPE_BITS        4
35 #define CQ_DESC_TYPE_MASK        ((1 << CQ_DESC_TYPE_BITS) - 1)
36 #define CQ_DESC_COLOR_MASK       1
37 #define CQ_DESC_COLOR_SHIFT      7
38 #define CQ_DESC_Q_NUM_BITS       10
39 #define CQ_DESC_Q_NUM_MASK       ((1 << CQ_DESC_Q_NUM_BITS) - 1)
40 #define CQ_DESC_COMP_NDX_BITS    12
41 #define CQ_DESC_COMP_NDX_MASK    ((1 << CQ_DESC_COMP_NDX_BITS) - 1)
42 
43 static inline void cq_desc_dec(const struct cq_desc *desc_arg,
44 	u8 *type, u8 *color, u16 *q_number, u16 *completed_index)
45 {
46 	const struct cq_desc *desc = desc_arg;
47 	const u8 type_color = desc->type_color;
48 
49 	*color = (type_color >> CQ_DESC_COLOR_SHIFT) & CQ_DESC_COLOR_MASK;
50 
51 	/*
52 	 * Make sure color bit is read from desc *before* other fields
53 	 * are read from desc.  Hardware guarantees color bit is last
54 	 * bit (byte) written.  Adding the rmb() prevents the compiler
55 	 * and/or CPU from reordering the reads which would potentially
56 	 * result in reading stale values.
57 	 */
58 
59 	rmb();
60 
61 	*type = type_color & CQ_DESC_TYPE_MASK;
62 	*q_number = le16_to_cpu(desc->q_number) & CQ_DESC_Q_NUM_MASK;
63 	*completed_index = le16_to_cpu(desc->completed_index) &
64 		CQ_DESC_COMP_NDX_MASK;
65 }
66 
67 #endif /* _CQ_DESC_H_ */
68